Method of preventing the caking of hardened oil coated particles

ABSTRACT

A method of preventing the caking of hardened oil coated particles which comprises allowing particles consisting of a core material coated with a coating agent predominantly of a hardened oil having a melting point of 45*- 85*C., to stand for at least 20 hours at a temperature exceeding 25*C. but lower than the softening point of the hardened oil to thereby stabilize the crystal structure of the hardened oil and thereafter adding to the coated particles a caking inhibitor, in an amount of 0.3 - 5 percent by weight based on weight of the coated particles.

United States Patent [19*] Ueno et al. Aug. 28, 1973 [54] METHOD OFPREVENTING THE CAKING 2,945,764 7/1960 Lanz 99/4 X 01: ENE OIL COATEDPARTICLES 3,014,800 12/1961 Guidarelli 99/7 X 3,306,730 2/1967 Malmberget a1 117/100 A X Inventors: Ryulo Ueno, hm m y tsuya 3,313,615 4/1967Formaini 117/100 A x Miyazakl, ltami; Shigeo lnamine, 3,467,525 9/1969Hale et al. 99/2 Nishinomiya, all Of Japan 3,484,250 12/1969 Vollink etal. 99/83 o 3,615,647 10/1971 Kassens 117/100 A X [73] Ass1gnee: UenoFlne Chemlcal lndustrles, Ltd.,

Osaka Japan Primary Examiner-William D. Martin [22] Filed; J l 21, 1971Assistant ExaminerShive P. Beck An Sh a d Sh ll 21 Appl. No.3 164,717 na [57] ABSTRACT Foreign Application Data A method of preventing thecaking of hardened oil July 24, 1970 Japan 45/64294 coated particleswhich comprises allowing particles consisting of a core material coatedwith a coating [52] US. Cl 117/16, 99/140 R, 99/143, agent predominantlyofa hardened oil having a melting I 117/100 A point of 4585C., to standfor at least 20 hours at a [51] Int. Cl. B440 1/06, B44d 5/08temperature exceeding 25C. but lower than the soften- [58] Field ofSearch 117/100 A, 167, 16; ing point of the hardened oil to therebystabilize the 99/140, 156, 83, 140, 2 F, 143, 159 crystal structureofthe hardened oil and thereafter adding to the coated particles acaking inhibitor, in an [56] References Cited amount of 0.3 5 percent byweight based on weight v UNITED STATES PATENTS of the coated particles.

1,985,846 12/1934 'lrowbridge 99/156 6 Claims, 2 Drawing FiguresEXOTHERM ENDOTHERM C FORM Patented Aug. 28, 1973 2 Sheets-Sheet 1 B FORMzmwzkoozw I... 25:56

Pntanted Aug. 28,1973 3,754,961

2 Sheets-Sheet 2 l 1 l l l I 4000 3000 2000 I500 I000800600400 METHOD OFPREVENTING THE CAKING OF HARDENED OIL COATED PARTICLES This inventionrelates to a method of preventing the caking of particles consisting ofa core material coated with a coating agent whose principal ingredientis a hardened oil.

Hardened oils have been used for such purposes as the prevention ofmoisture absorption, maintenance of effectiveness of prevention ofreaction of such drugs and chemicals as medicines for man as well asanimals, agricultural chemicals, food additives, etc., by serving as asurface coating with these drugs and chemicals as the core material.Especially when a food additive is the core material, the application ofa hardened oil coating has been frequently practiced to achieve a uniqueend, i.e., to prevent the additive from eluting at room temperature butpermitting it to elute during the step of heating the food product, inorder to prevent the decomposition of the core material in the foodstuffmaterial and any adverse effect of the core material on the foodstuffmaterial.

A hardened oil to be used for the above described purposes is one havinga melting point ranging from 45 to 85C. In the case of a hardened oilwhose melting point is below the foregoing range, there is thepossibility of its softening at high temperatures experienced in summer.Especially desirable hardened oils are, for example, hardened beeftallow (m.p. 59 61C.), hardened whole oil (m.p. 55 60C.), hardened rapeseed oil (m.p. 50 62C.), hardened soybean oil (m.p. 60 69C.), hardenedcottonseed oil (m.p. 55 61C.) and hardened castor oil (m.p. 82 85C.)

As methods of coating such core materials as medicines for man as wellas animals, agricultural chemicals and food additives with a hardenedoil numerous methods are known such as the following l. The sprayingmethod which comprises heatmelting the hardened oil, dispersing the corematerial therein and thereafter spraying this dispersion into a gas of amelting point below that of the hardened oil (e.g. air, nitrogen andcarbon dioxide) thereby accomplishing the coating of the core materialand at the same time the cooling and solidification of the particles.

2. The coating pan method in which the coating of the particles iscarried out by repeating an operation consisting of placing the corematerial in a coating pan, spraying a solvent-dissolved hardened oilonto the core material while tumbling same in the pan, and thereafterevaporating and removing the solvent by blowing, for example, hot airagainst the coated particles.

3. The suspensiomin-air coating method which comprises floating the corematerial in a stream of air and coating the so floating core material byspraying a solution of a hardened oil against the material.

4. The vacuum vaporization method which'comprises heating the hardenedoil in a vacuum and evaporating it against the core material to therebyeffect the vapor deposition of the hardened oil onto the surface of thecore material.

5. The electrostatic coating method which comprises impressing theparticles of the core material and the particles of the hardened oilsolution with opposite electric charges to thus unite these particles.

6. The meltable-dispersion method which comprises heat-melting thehardened oil in a liquid which does not dissolve the same, dispersingthe core material in the melt, forming the dispersed core material intosmall particles, and thereafter cooling and solidifying the same.

While the particle size of these coated particles consisting ofa corematerial coated with a hardened oil will vary depending upon theintended use of the core material, the coated particles are usuallyprepared so as to have a suitable particle diameter ranging from 50 to2,000 microns. It is most desired that these coated particles areindependent from each and have fluidity. If the coated particles arecaked and in a lumpy state, their use is not only inconvenient but alsothis makes them unfit for use at times. Especially in the case where thecore material happens to be a food additive, it is necessary that theseparticles are uniformly mixed in the foodstuff material. Therefore, afood additive in which the particles are in a caked state rather thanachieving its purpose has the opposite effect of degrading the qualityof the food, since it becomes incorporated in the food product in anonuniform state.

In view of the foregoing reason, in order to prevent this caking whichcauses an excessive degradation of the merchandise value of the product,the addition of about 0.3 5 percent by weight based on the hardened oilcoated particles of a finely divided inorganic substance such as silica,magnesium alumino silicate, magnesium carbonate, and calcium tertiaryphosphate or alkaline earth metal salts of higher fatty acids, such ascalcium stearate or magnesium stearate is being practiced. However,notwithstanding the addition of these caking inhibitors, it frequentlyhappens that the product becomes caked after shipment of the productfrom the manufacturers plant and by the time it reaches the consumer.

The object of the present invention is to therefore provide hardened oilcoated particles in which the hereinbefore noted caking does not occur.

On the basis of a finding that the hereinbefore described caking of thehardened oil coated particles was due to a change taking place in thecrystal structure of the hardened oil used as the coating agent, it waspossible to achieve the above object of the invention by. operating inthe following manner. The particles consisting of a core material whichhave been coated with a coating agent whose principal ingredient is ahardened oil of a melting point 45 C. are allowed to stand for at least20 hours at a temperature higher than 25C. but lower than the softeningpoint of the hardened oil, thereby stabilizing the crystal structure ofthe hardened oil, following which the particles are incorporated with acaking inhibitor, in an amount of 0.3 5 percent by weight based on theweight of the coated particles.

Changes in the crystal structure of a hardened oil occur as a result ofits temperature history. That is, the solidified mass of hardened oil ismade up of a plurality of crystals, i.e., a congregation of smallcrystals and, thus, changes in the crystal structure take place as aresult of the temperature history of these small crystals. The solidhardened oil obtained by either cooling and solidifying or precipitatingfrom a solvent a hardened oil which is in a molten state as a result ofheating is of a structure in which a plurality of small crystals in anunstable form are collected together in a relatively loose arrangement.Now, when these crystals are allowed to stand for a prolonged period oftime in a state where heat is applied from the outside, the unstablecrystal structure is tranforrned to a stable crystal structure andmoreover the small crystals which were in a relatively loose arrangementbecome disposed orderly and in a state, with a consequence that theybecome exceedingly stabilized.'The crystal structure which has beenstabilized in this manner no longer changes at a temperature lower thanthe softening point of the hardened oil.

The changes, such as discribed, in the crystal structure of a hardenedoil due to its temperature history have been examined in detail by meansof differential thermal analysis or X-ray or infrared absorptionanalysis. I-Iowever, no studies have been made which relate theprevention of the caking of the hardened oil coated particles to thecrystal structure of the hardened oil. The studies concerning theprevention of caking have completely ignored the crystal structure ofthe hardened oil but have been exclusively directed to inquires withregard to the classes and amount of the caking inhibitor to be used.Further, the explanation that was given regarding the cause of thecaking was merely that a part of the hardened oil melts on approaching atemperature close to the softening point, thereby causing a fusion totake place between the particles and thus result in a cal ced state. Asa result of research concerning the relationship between the changes inthe crystal structure of the hardened oil and caking, it has been foundthat the caking of the hardened oil coating particles was not onlyaffected by the temperature at which the particles were allowed to standbut that the temperature history of the coated particles also had agreat effect on this caking phenomenon.

When the relationship of the changes in crystal structure and caking isdescribed with reference to the accompanying drawings, taking as anexample hardened beef tallow, it is as follows In the accompanyingdrawings,

FIG. 1 is a graph illustrating the results of a different thermalanalysis of hardened beef tallow; and

FIG. 2 is a graph illustrating the results of an infrared absorptionanalysis of hardened beef tallow.

When a differential thermal analysis is carried out on hardened beefvtallow (m.p. 59 61C.) after heatmelting it and then cooling andsolidifying it, three classes of curves are obtained as shown in FIG. Idepending upon the method employed for the cooling treatment. Thecrystal forms of the hardened oil which pro vide these three classes ofdifferential thermal curves are referred to as A, B and C forms. The Aform crystal is a crystal form obtained when a heat-melted hardened oilis rapidly cooled and solidified in cold water, and while it is stableat low temperatures, it gradually transform to the B form crystal whenthe temperature rises finally becoming transformed to the C formcrystal. The B form crystal is one which is obtained when the hardenedoil has been cooled and solidified under relatively mild conditions,i.e. by being allowed to stand at room temperature. Under theseconditions, the B form crystal is obtained without passing through the Aform crystal stage. The B form crystal, as in the case with the A formcrystal, is unstable and therefore gradually transforms to the C formcrystal. The C form crystal is a crystal form'which is obtained when theA and B form crystals have been allowed to stand either for or more daysat C. or 3 or more days at C. This C form crystal being exceedinglystable does not change at temperatures below the softening point.Further, concurrently with this transformation, a change in thedisposition of the small crystals from a loose arrangement to an orderlyarrangement takes place. Therefore, not only is the crystal formstabilized but also the stability of the overall structure is increased.Referring to the graph of FIG. I, the maximum peak temperature of the Aform crystal is 68C., that of the B form crystal is 64C. and that of theC form crystal is 70C., that of the C form crystal being the highest,while that of the B form crystal being the lowest. That is, in the caseof the hardened beef tallow, the transformation takes place first fromthe A form crystal to the Bform crystal having a lower maximum peaktemperature and then to the C form crystal which is the most stable.This sort of transformation is a phenomenon which is generally seen inthe case of the higher fatty acids and higher alcohols. In FIG. 2, graphI illustrates the infrared analysis results of the C form crystal andgraph II shows that of the A form crystal. The form of graph I is morecomplicated than that of graph II, and it can be clearly seen adifference exists.

In general, the hardened oils precipitated from a solvent are of the Cform crystal, but in this case it is still an unstable C form crystal.In addition, its crystal structure is also one not disposed in anorderly manner but is one which is of loose arrangement. However, whenthis hardened oil is allowed to stand at above a certain temperature,the crystals are changed to C form crystals having stability and itscrystal structure becomes one which has an orderly arrangement.

Graph III of FIG. 2 is the result of an informed analysis of hardenedbeef tallow which has been crystallized by the evaporation of chloroformfrom a chloroform solution at 20C., a clear difference being seen fromthis graph when compared with graphs l and II. When this hardened oilcrystal is allowed to stand at above a certain temperature, it changesto a stable crystal equalling that of graph I.

The speed with which the crystal structure transforms from the A or Bform to C form is influenced by the temperature at which the crystalsstand, the speed becoming faster in proportion as the temperaturebecomes higher. At low temperatures at which the transformation does notprogress (generally, the speed becomes very slow when the temperaturefalls to below 15C.), caking of the particles coated with a hardened oilof the A form or B form crystals does not take place even though theparticles are allowed to stand fora prolonged period of time.

The caking of the hardened oil coated particles, which takes place whenthe crystal structure transforms from the A or B form to the C form, canbe explained as being a phenomenon wherein particles combine by mutuallytaking in the crystals of the other particles at the surfaces thereofduring the time when the transformation of the A form and B formcrystals to the stables C form crystal is taking place or when a changein the loose disposition of the small crystals to an orderly arrangementis taking place.

In carrying out the stabilization of the hardened oil crystal structurein accordance with the present invention, i.e., the transformation fromthe A form and B form crystals to the C form crystal as well as thechange in the loose disposition of the small crystals to an orderlyarrangement, the hardened oil coated particles are suitably allowed tostand at a temperature above 25C., and preferably above 30C. At lowtemperature of below 25C., either the speed of transformation is hasoccurred during the transformation is eliminated.

The particles, which have in this way been rendered independent of eachother, as then incorporated with 0.3 5 percent by weight, and preferably0.5 3 percent by wieght, based on the particles, of a caking inhibitor,and as a result the product of the present invention of improvedfluidity, which does not cake at temperatures lower than the softeningpoint of the hardened oil, and is therefore of high merchandise value isobtained. While any substance may be used as the aforesaidcaking-inhibitor as long as it is one which does not impede the functionof the core material, usually silica, magnesium alumino silicate,magnesium carbonate, calcium tertiary phosphate, calcium stearate ormagnesium stearate is conveniently used.

The operation for carrying out the stabilization treatment is simple.For example, the coated particles immediately after their preparationneed only be allowed to stand in a room of a temperature higher than25C.

but lower than the softening point of the hardened oil untiltransformation of the crystal structure to the form C form is completed.This is done with the particles spread thinly in a vessel, such as apan, in such a manner that the particles are subjected to a minimum ofload. The reason not to impose a load more than the minimum on theparticles is to reduce as much as possible the occurrence of cakingduring the transformation stage. Since it is impossible to avoid cakingfrom taking place during the transformation, a pressure which tends toincrease the contact area between the particles at the coated particlesusing a customary mixer will do. The slight caking which has occurredduring the stabilization treatment is completely eliminated during thismixing while at the same time the caking inhibitor becomes uniformlymixed with the coated particles. Thus, coated particles having fluidityand in which caking does not take place can be readily obtained.

The following non-limitative examples are given for more specificallyillustrating the invention. The percents in the example are on a weightbasis.

EXAMPLE 1 Four kg of hardened beef tallow were heat-melted andmaintained at a temperature of 70C. After adding 1 kg of powdered sorbicacid to the melted hardened beef tallow, the mixture was mixed withthorough stirring using a homo-mixer to obtain a homogeneous dispersion.The dispersion was sprayed into air of 20C., and on cooling andsolidification hardened oil coated sorbic acid particles useable as afood preservative were prepared. The following caking test was carriedout on the so obtained coated particles.

The several classes of caking inhibitors indicated in Tables l--l to 1-5were added separately to the coated particles, following which thecoated particles were allowed to stand under the various conditionsindicated in Tables l-l to [-5. This was followed by packing the coatedparticles in a cylindrical tube 40 mm in diameter and mm in height andsubjecting the particles to a pressure by placing a 500-gram weight atopthe packed particles. The particles were allowed to stand for 7 days inthis state at the prescribed test temperatures indicated in Tables ll to1-5. Next, the coated particles contained in the tube were taken outtherefore ensuring that in doing so the caked condition of the particleswas not disturbed, after which the so withdrawn particles were lightlysieved with a lO-mesh sieve. The amount of coated particles remaining onthe sieve relative to the total amount was then calculated and expressedin percent. This value, which is' designated the degree of caking isindicated in Tables l'-l to l-5. The larger this value is, the greaterthe caking of the particles. Also shown in Tables ll to l5 are thecrystal forms of the hardened beef tallow before and after the test.

TABLE 1-1 Test Crystal form temper- Degree of Class and amount of cakinginhibitor ature caking Before After Conditions under which particles areallowed to stand added C.) (percent) test test Testd immediately afterpreparation o Calcium tertiary phosphate, 3% Silica, 3% C Magnesiumalumino silicate, 3%..

'IAlilrl'i 1! Test temper Degree Class and amount of caking inhibitornmre caking Condition under which particles are allowed to stand addedC. perm-Ht Leitlstanding 2 days at 25 C. after preparation 38 o. r r

Calcium tert 3 phosphate, 3O Silica, 3% 30 Magnesium alumino silicate,3% 30 TABLE 1-3 Test Crystal form temper- Degree of Class and amount ofcaking inhibitor ature caking Before After Condition under whichparticles are allowed to stand added C.) (percent) test test C c C C C CTABLE 14 A Test Crystal form temper- Class and amount of cakinginhibitor ature Before After Condition under which particles are allowedto stand added 0.) test test Left standing 3 days at 30 C. afterpreparation Calcium tertiary phosphate, 0.5% 30 C C D Silica, 0.5% 30 CC D Magnesium alumino silicate, 0.5% 30 C C Do Calcium tertiaryphosphate, 2%. 30 C .C

TABLE 1-5 Test Crystal form temper- Degree of Class and amount of cakinginhibitor ature caking Before After Condition under which particles areallowed to stand added C.) (percent) test test Loft standing hours at 45C C a .Y 1 I 0 Calcium tertiary phosphate, 2% 35 Below 1 v C Silica, 2%35 do Do. Magnesium alumino silicate, 2% 35 do. 0

EXAMPLE 2 EXAMPLE 3 The three kilograms of hardened castor oil (m.p. 8085C.) were heat-melted. After adding 4 grams of soya-lecithin thereto asa surfactant, one kg of finely divided fumaric acid was added, followingwhich the mixture was commingled with thorough stirring to obtain adispersion. While maintaining this dispersion at 90C., it was sprayedinto air of C., wherefrom it was cooled and solidified. As a resulthardened castor oil coated fumaric acid particles were prepared.

The so obtained coated particles were incorporated separately with thevarious caking inhibitors indicated in Table 2 to adhere the cakinginhibitors to the surface of the hardened caster oil coated fumaric acidparticles, and a caking test was carried out as in Example 1 under thevarious conditions indicated in Table 2. The results obtained are shownin Table 2.

The hardened castor oil coated fumaric acid particles are added to thestarting food material, and by preventing the elution of the fumaricacid at room temperature but by causing the acid to elute during theheating step, they are used for the purpose of lowering the pH of thefood product. Since as shown in Table 2 the degree of caking of theinvention coated particles is low, they are especially suitable for thispurpose.

TABLE 2 Test Degree Conditions under which Class and amount temperof theparticles are of caking inhibitor ature caking allowed to stand addedC.) (percent) Tested immediately after 10 5540.

preparation.

Do 80-85. Do Magnesium alumino 35 70-80. silicate, 2%. Do Calciumtertiary 35 70-80.

phosphate, 2%. Do 'lica, 2% 35 7080. Left standing 2 days at 10 5-10.

C. after preparation.

Do 35 5-10. Do Magnesium alumino 35 Below 1.

silicate, 2%. Do Calcium tertiary 35 Do.

phosphate, 2%. Do Silica, 2% 35 Do.

A glutamic acid powder of 40-mesh was placed in a coating pan and whilebeing tumbled the powder was sprayed with a 30 percent chloroformsolution of hardened beef tallow (mp. 59 61C.) After continuing thetumbling of the powder particles for a while and having accomplished theuniform wetting of the surface of the glutamic acid powder particles,the chloroform was evaporated by means of hot air. The foregoingoperation was repeated until the content of the hardened beef tallow inthe particles became 40 percent. As a result coated glutamic acidparticles which could be used as a seasoning as well as a pH loweringagent of food products were prepared.

The so obtained coated glutamic acid particles were allowed to standunder the conditions indicated in Table 3, after which the variouscaking inhibitors were added and the caking test was carried out. Theresults obtained are shown in Table '3.

TABLE 3 Test Degree Conditions under which Class and amount tcniperofthe particles were of caking inhibitor ature caking allowed to standadded C.) (percent) Tested immediately after 10 10-15.

preparation.

Do 35 60-70. Do Calcium stearate, 3%.. 35 4050. Do Mggnesium stearate,35 4050.

,0 D0 Magnesium 35 4050.

carbonate, 3%. Lclt sanding 3 days at l0 VH5. 37 Do 35 l0 15.

Do (lai -lulu si ziraln, 35 fir-luv. i.

' 3'2. l)o Magnesium sfl'aratv, 35 Ho.

3'71. Do Magnesium 3.5 Do.

carbonate, 3%.

From the results presented in the foregoing tables, it is seen that thecaking of the hardened oil coated particles is pronounced at the timethe crystal structure changes, with the consequence that unless thecrystal structure of the hardened oil has been stabilized the cakinginhibitor which has been incorporated in the coated particles ispractically powerless in demonstrating its effectiveness. On the otherhand, it is seen that in accordance with the invention method whereinthe caking inhibitor is incorporated in the hardened oil coatedparticles after having stabilized the crystal structure of the hardenedoil by allowing the coated particles to stand at a temperature higherthan 25C. but lower than the softening point of the hardened oil, theeffectiveness of the caking inhibitor can be fully demonstrated andstable hardened oil coated particles which have fluidity and do not cakeat normal temperatures can be obtained.

We claim:

1. A method of preventing the caking of hardened oil coated particleswhich comprises allowing particles consisting of a core material coatedwith a coating agent predominantly of a hardened oil having a meltingpoint of 45-85C., to stand for at least 20 hours at a temperatureexceeding 25C. but lower than the softening point of said hardened oiland thereafter adding to the stabilized hardened oil-coated particles acake inhibitor, in an amount of 0.3-5 percent by weight based on theweight of the stabilized hardened oil-coated particles.

2. The method of claim 1 wherein said caking inhibitor is a finelydivided inorganic substance.

3. The method of claim 1 wherein said caking inhibitor is an alkalineearth metal salt of a higher fatty acid.

coated particles.

III t i

2. The method of claim 1 wherein said caking inhibitor is a finelydivided inorganic substance.
 3. The method of claim 1 wherein saidcaking inhibitor is an alkaline earth metal salt of a higher fatty acid.4. The method of claim 1 wherein said caking inhibitor is silica,magnesium alumino silicate, magnesium carbonate, tertiary calciumphosphate, calcium stearate or magnesium stearate.
 5. The method ofclaim 1 wherein said core material coated with said hardened oil isallowed to stand at a temperature exceeding 30*C.
 6. The method of claim1 wherein said caking inhibitor is added in an amount of 0.5-3 percentby weight based on the weight of the stabilized hardened oil-coatedparticles.